The application is a U.S. national stage application of copending International Application Serial No. PCT/JP01/01766 filed Mar. 7, 2001 and published in a non-English language.
This invention relates generally to a crawler vehicle and, more particularly, to an improvement in a snow-removing machine.
A crawler vehicle having at its front portion a working member (snow-removing section) is disclosed in, for example, Japanese Patent Publication No. SHO-51-30378 entitled xe2x80x9cSnow-Removing Machinexe2x80x9d. This snow-removing machine comprises a body frame connected to a rear portion of a crawler frame, which has a front portion equipped with a driven wheel and a lower portion equipped with two guide wheels, through a pivot shaft for vertical swinging movement, a snow-removing section mounted at a front portion of the body frame and serving as a working member, an engine mounted on the body frame, a drive wheel mounted to a rear portion of the body frame, and a crawler belt trained around the drive wheel, the driven wheel and the guide wheels.
In addition, during traveling of the crawler vehicle with its snow-removing section held in an inoperative state, a jack is extended to allow the body frame to swing clockwise about the pivot shaft, lifting the snow-removing section to thereby prevent the snow-removing section from hitting an obstacle on the road surface.
FIGS. 6A and 6B hereof are schematic side elevational views showing operations of the aforementioned conventional snow-removing machine. More specifically, FIG. 6A shows that the snow-removing machine in snow removing operation, while FIG. 6B shows a state in which a jack 101 remains in an extended condition to allow a body frame 103 to swing clockwise about a pivot shaft 102 such that a snow-removing section 104 is lifted.
When the snow-removing section 104 is lifted, a drive wheel 105 moves downward as shown by arrow {circle around (1)}. As a result, the distance M between the center of a driven wheel 106 and the center of the drive wheel 105 slightly varies such that the distance N between the center of the drive wheel 105 and the center of the rearmost guide wheel 107 decreases. As the distances M and N vary in such a manner, tension of a crawler belt 108 also varies. When the tension of the crawler belt 108 exceeds an excessive level, the crawler belt 108 encounters a breakdown. In contrast, when the tension of the crawler belt 108 is too small, the crawler belt 108 is apt to be dislocated from the drive wheel 105 or the driven wheel 106.
Now, discussion will be made as to an operation of the snow-removing machine when it accidentally runs on hard snow during snow-removing operation with reference to FIGS. 7A to 7C.
In FIG. 7A, the crawler belt 108 is held in close contact with road surface 100, with the body frame 103 and an auger 104 located at the front portion of the crawler vehicle being held at a given height from the road surface 100 by the action of a pivot shaft 102 mounted at a rear portion of a crawler frame 109 located inside the crawler belt 108 and the jack 101 located forwardly of the pivot shaft 102. Reference numeral 110 designates a sleigh which serves as a member for suitably maintaining the auger 104 at the given height from the road surface 100 or as a member for reducing weight and load of the auger 104 to be applied to the body frame 103. A pentagon is formed by connecting the sleigh 110, the auger drive shaft 112, the pivot shaft 102, the center of the guide wheel 107, and the sleigh 110 (hereinafter referred to as a xe2x80x9cpentagon Xxe2x80x9d).
It has been proposed to provide a snow-removing practice wherein, when an object to be removed is new snow, the auger 104 is intentionally lowered with a view to remove an increased amount of snow. In such a practice, the jack 101 is retracted to allow of the body frame 103 to rotate counterclockwise about the pivot shaft 102, thereby lowering the auger 104.
However, when the snow-removing machine accidentally comes across hard snow with the jack 101 held in the retracted state, the snow-removing machine encounters the following problems. In this event, the sleigh 110 runs on hard snow, causing the crawler belt 108 to be lifted up from the road surface 100 in the vicinity of the driven wheel 106. That is, the crawler belt 108 is caused to rotate clockwise as a whole at an angle xcex81 about the pivot shaft 102. In parallel with such a movement, the pentagon X shown in FIG. 7A varies in a manner as described below.
The center 107 a of the guide wheel 107 is caused to swing clockwise at the angle xcex81 about the pivot shaft 102. Since, in this instance, the center 107a remains at a fixed height from the road surface 100, the pivot shaft 102 is lowered. Since, in this event, the sleight 110 and the body frame 103 form a common rigid structure to which the auger shaft 112 and the pivot shaft 102 are interconnected, the line segment connected between the sleigh 110 and the auger shaft 112 and the line segment connected between the auger shaft 112 and the pivot shaft 102 intersects at an angle xcex1 which remains unchanged at a constant value.
When the pivot shaft 102 is lowered with the angle xcex1 held constant, the auger shaft 112 is apt to swing clockwise about the sleigh 110, causing the auger shaft 112 to rise. Pentagon formed during such a movement is referred to as the pentagon Y.
FIG. 7C shows the pentagons X and Y in an overlapped state. When the center 107a is caused to swing clockwise at the angle xcex81 about the pivot shaft (provided that, since the level of the center 107a remains unchanged, the pivot shaft 102 swings clockwise about the center 107a by appearance), the pivot shaft 102 is lowered by the distance xcex941 and, in link motion therewith, the auger shaft 112 swings clockwise at the angle xcex82 about the sleigh 110, thereby lifting up the auger shaft 112 by the distance xcex942.
Thus, when the auger shaft 112 is raised and the pivot shaft 102 is lowered, the auger 104 shown in FIG. 7B is tilted upward more than that shown in FIG. 7A, thereby deteriorating biting effect of the snow.
As discussed above, in the conventional snow-removing machine, if the auger is lowered when the snow-removing machine removes snow deeply, the auger is apt to be tilted upward with a resultant decrease in performance efficiency of the snow-removing operation.
It is therefore an object of the present invention to provide a crawler vehicle which has an improved performance efficiency in snow-removing operation and is able to minimize the variation in tension of a crawler belt.
According to an aspect of the present invention, there is provided a crawler vehicle comprising a crawler frame having a front portion carrying a driven wheel and a lower portion carrying at least one lower idle wheel, a body frame connected vertically swingably to a rear portion of the crawler frame, a working member mounted to a front portion of the body frame, an engine mounted to the body frame, a drive wheel mounted to a rear portion of the body frame, and a crawler belt trained around the drive wheel and the driven wheel, characterized by a pivot shaft positioned forwardly of the lower idle wheel for allowing the vertical swinging movement of the body frame.
When the front portion of the crawler belt is lifted up from the road surface, the center of the lower idle wheel is apt to swing about the pivot shaft. Since, in this event, the pivot shaft is located forwardly of the lower idle wheel, the swing movement of the lower idle wheel causes the pivot shaft to be lifted. Due to this lifting movement of the pivot shaft, the auger shaft swings about the sleigh and is lowered. Consequently, it is possible for the auger to be lowered regardless of soft snow or hard snow, thereby carrying out snow-removing operation in an efficient manner.
In a preferred form, the lower idle wheel comprises a plurality of lower idle wheels while the pivot shaft is located forwardly of a lower rearmost one of the idle wheels. However, the pivot shaft should be positioned rearward of a lower idle wheel which is located next to the rearmost lower idle wheel at a front area thereof.
It is desirable that the pivot shaft for connecting the body frame to the crawler frame is positioned forwardly of the lower idle wheel, the drive wheel is positioned rearwardly of the lower rearmost idle wheel, the lower idle wheel is positioned at a lower intermediate position between the pivot shaft and the drive wheel, and an upper idle wheel is mounted to the crawler frame for supporting the crawler belt at an upper intermediate position between the pivot shaft and the drive wheel.
By connecting the body frame to the crawler frame with the pivot shaft, the body frame is enabled to arbitrarily swing, thereby allowing the front working member to be adjusted in height relative to ground surface or road surface. During such an adjustment, although the drive wheel is raised or lowered, provision of the additional upper idle wheel allows the total length of the crawler belt to be maintained at a substantially constant value for thereby minimizing the variation in tension to be exerted to the crawler belt. This results in remarkably extended life of the crawler belt.
In a specific form, the working member comprises a snow-removing section. More specifically, it comprises an auger or a blade for pushing and removing earth and sand as well as arable soil.